Wet to bisque to glaze-fired size — with reverse calc to hit a target finished dimension.
Bisque-fired size
10.99 in
Glaze-fired size
10.56 in
Total shrinkage
12.0%
Clay shrinks twice — roughly 70% of the total happens between leather-hard and bisque as physical water leaves, and the remaining 30% during the glaze fire as the body vitrifies.
Porcelain moves the most (12-14%), stoneware sits around 10-12%, earthenware is the most forgiving at 6-8%. Always run a shrinkage test bar on a new clay body — published numbers vary by supplier and firing cone.
glaze_size = wet × (1 − shrink ÷ 100)
bisque_size = wet × (1 − 0.7 × shrink ÷ 100)
wet_needed = target ÷ (1 − shrink ÷ 100)